Recently, multiple system cable operators (MSOs) have been providing ever increasing numbers of variable bit-rate (VBR) video, particularly as on-demand high-definition content. The instantaneous bandwidth usage of the compressed VBR video scales with the varying complexity of the video content and thus, the VBR videos are typically transmitted in short, uneven spurts of data. For instance, high definition VBR videos can reach instantaneous rates approaching 16 Mbps for MPEG2 compression and 8 Mbps for MPEG4 Advanced Video Coding compression.
Due to the uneven bandwidth utilizations associated with transmission of VBR videos, it is often difficult for the MSOs to achieve a high average channel utilization for multiple VBR video flows. For instance, situations often arise where the total bandwidth for the multiple VBR video flows exceeds the capacity of the channel, which substantially limits the number of VBR video flows that can be transmitted over the channel. In addition, if the average of the sum of the instantaneous VBR video flows is close to the capacity of the channel, there may be unacceptable delays in some of the video packets, degrading the operation of the video decoders. A proposed solution is channel bonding, which increases bandwidth to improve statistical multiplexing of video flows; however, channel bonding is oftentimes prohibitively expensive to implement.
Attempts at maximizing the channel capacity have also led to capping of the amounts of bandwidth each of the multiple VBR video streams are allotted. Other attempts have led to encoding of the VBR videos at constant bit rates. While both of these options reduce the problem with statistical multiplexing, they also degrade the signal-to-noise ratio of the video and thus degrade its quality.
It would thus be beneficial to achieve a relatively high average channel usage in the transmission of multiple VBR videos, without suffering from the disadvantages associated with conventional VBR video transmission techniques.